Ability to specify user name in Webdav path despite UUID mode

[PVince81]

Since #409 and cs3org/reva#1052 the Webdav path is now requiring UUIDs instead of user name.

However, @butonic said that we should also supposed specifying a user name there.

This ticket is to track this task / discussion.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 10 days if no further activity occurs. Thank you for your contributions.

[fschade]

Please open again if the ticket is still relevant